Method for transmission of information between nodes of a network and network using said method

ABSTRACT

A method for communication between nodes (UR 1;  UR 2;  UC 1 -UC 16 ) of a network, interconnected by a transmission channel and each identified by a node identification number in which at least one transmitter node emits at least one message to at least one message recipient node. The message comprises a description of a path (PH) between the transmitter node which emits the message and the message recipient node. The path is defined by the node that emits the message via a sequence of node identification numbers along the path itself.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation and claims benefit of U.S. patentapplication Ser. No. 11/910,828, filed Apr. 6, 2005, and claims benefitof International Application No. PCT/IT2005000189, filed Apr. 6, 2005,now expired, all of which are hereby incorporated by reference in theirentirety.

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the reproduction of the patent document or the patentdisclosure, as it appears in the U.S. Patent and Trademark Office patentfile or records, but otherwise reserves all copyright rights whatsoever.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING OR COMPUTER PROGRAM LISTING APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

This invention concerns in general the communication of messages, i.e.data packages, between nodes or units interconnected by a transmissionchannel, for example the nodes of an electrical network on which thenodes transmit messages by means of carrier waves.

WO-A-2004/088871 describes a method for transmission of messages betweenan information collecting unit and a plurality of control units,combined with electrical equipment, for example lighting points in anurban area. The method provides for a particular method of transmittingthe messages also over long distances in the presence of noise on thetransmission channel, which in said case is represented by theelectrical distribution network.

U.S. Pat. No. 4,692,761 describes a method for the transmission ofinformation from reading units combined with electricity meters to acollecting unit. Each node combined with a meter sends the meter readinginformation to a collecting node by means of a complicated system fordetermination of the message path. In practice, the emitter node sendsthe message to a node below, chosen from a plurality of possible nodesbelow. This node below that receives the message forwards it again tothe collecting unit by means of an analogous procedure, i.e. by choosinga node below it from a plurality of possible nodes below. In practice,the message path is determined in an adaptive manner step by stepaccording to the conditions of the line, for example according to thenoise present on the various portions of the electrical network alongwhich the messages are propagated by means of carrier waves. This systemis obviously very complex.

SUMMARY OF THE INVENTION

The object of this invention is to provide a method for the transmissionof messages, i.e. data packages, which is easy to implement and at thesame time suitable for transmitting data, as information or commands,also in complex networks, for example electricity distribution networksin urban areas with a very high number of nodes and interconnections,along a channel (represented by the same electrical network) which canhave an impedance that varies over time and therefore unpredictabletransmission conditions.

Substantially, the invention provides for a method for communicationbetween nodes of a network, interconnected by a transmission channel andeach identified by a node identification number, in which at least onetransmitter node emits at least one message to at least one messagerecipient node, and in which the message comprises a description of apath between said transmitter node that emits the message and saidmessage recipient node, said path being defined, by the node emittingthe message, by means of a sequence of node identification numbers alongsaid path.

A transmission method of this type can be implemented simply andefficiently to transmit data, information, commands or in general anytype of message consisting of a bit package along an electricitydistribution network, via carrier waves, over extensive distances fromthe transmitter node, and also in the presence of considerableinterference on the network. Contrary to what occurs in other knownsystems, designed to transmit information on complex networkscharacterized by a high number of interconnections, in the methodaccording to the invention the message is auto-descriptive, i.e. aportion of it contains the entire description of the path it must followto reach the recipient node. This description is provided by thesequence of the identification numbers of the nodes via which themessage must pass to reach the recipient node. Since the distancebetween transmitter node and recipient node can be considerable, thenodes of the path regenerate the message by sending it to the next nodedefined by the path stored in the message.

To allow a node, which receives at random a message on the receptionchannel, to check whether it is the node to which said message must bedelivered, or whether it must be regenerated via an echo, according toan advantageous embodiment of the invention the messages comprise anidentification number of the next node along said path to which themessage must be transmitted, said identification number of the next nodeidentifying to which node of the path—defined in the message—saidmessage must be transmitted. The content of the field defined asidentification number of the next node is updated by each node thatreceives and retransmits the message (in the form of a reply or echo).

According to one embodiment of the invention the method provides for thefollowing:

-   -   when a message recipient node receives said message, it        generates a reply message addressed to the node that emitted the        message and containing a description of the path from the node        that receives the message to the node that has emitted the        message received;    -   when a node different from the message recipient node receives a        message in which the identification number of the next node is        different from its own identification number, said node remains        inert;    -   when a node receives a message in which the identification        number of the next node corresponds to its own identification        number, it generates an echo of the message, replacing the        identification number of the next node with the identification        number of the following node in the sequence of node        identification numbers defining said path.

To permit checking of the progress of the message along the pathdescribed in it towards the recipient node, each node that receives amessage from a node preceding it along the path defined in said messagecan advantageously send confirmation of reception of the message to saidnode preceding it. When a node does not receive a message ofconfirmation to its own message addressed to the following node alongthe path defined in said message, it can advantageously perform at leastone attempt at transmission of the same message to the node which, alongsaid path, is subsequent to the node from which the confirmation messagehas not been received. In fact, failure to receive the confirmationmessage can be due either to an impediment along the transmission lineor to a fault in the adjacent node (which therefore cannot respond witha reception confirmation message). In the first case also the subsequentattempts to transmit the message beyond the node that does not replywill be unsuccessful, while in the second case the message may skip thefaulty node and reach its destination all the same, when the conditionsof the transmission line permit it, i.e. when the nodes are sufficientlyclose to each other or the line is sufficiently clean. After a certainnumber of attempts at transmitting the same message, to consecutivenodes along the path defined in a message, the node generates a messagesignaling interruption of the path addressed to the transmitting node,so that the transmitting node can attempt to send the same message tothe same recipient node via a different alternative path.

According to an advantageous embodiment, particularly suitable in thecase of complex networks with many nodes and multiple connections, aplurality of collecting nodes and a plurality of control nodes can beprovided and said control nodes can be divided into a plurality ofgroups, each comprising a series of control nodes, each group beingassigned to a collecting node and the collecting node interrogating viasaid messages the control nodes assigned to it.

The following can also be provided:

-   -   each control node of a group is also assigned to an additional        collecting node;    -   if there are no faults on the collecting nodes, the control        nodes of each group communicate with the respective main        collecting node to which they are assigned;    -   in the event of a fault on said main collecting node, the        collecting nodes assigned to it are re-assigned at least        temporarily each to the respective additional collecting node.

This procedure guarantees the possibility of communication also in theevent of a fault in one or more of the collecting nodes.

The control nodes can consist of control units combined with electricalor electronic equipment connected to an electric distribution network,for example in a building, a complex structure such as a hospital, anairport or an urban area. Typical electrical equipment combined with thecontrol nodes can be lighting points powered by a distribution network.In said case the control nodes permit, via the respective control units,checking of correct operation of the electrical equipment combined witheach node. The collecting nodes, with respective collecting units, caninterrogate the individual control units combined with the respectivecontrol nodes and transmit to an alarm signal monitoring centre in theevent of a fault.

When the network is particularly complex, it can be advantageouslydescribed via a series of coverage equations, each of which defines asequence of control nodes connected to one another and to a collectingnode. The set of the coverage equations constitutes a topologicaldescription of said network.

The invention also concerns a network for the transmission ofinformation between nodes interconnected by said network, characterizedin that said nodes transmit messages via a method as defined above andbetter described below in a possible embodiment.

Further advantageous features of the invention are described in detailbelow with reference to implementation examples.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention may be better described by following the description andthe attached drawings which show practical non-limiting embodiments ofthe invention. More specifically, in the drawing:

FIG. 1 shows a simplified example of a small network according to oneembodiment of the invention, with two collecting units and plurality ofmeshes along which control units are distributed in the various nodes;

FIG. 2 shows a diagram of a control unit of a network according to anembodiment of the invention;

FIG. 3 shows a diagram of a collecting unit;

FIG. 4 shows schematically the structure of a message used forcommunication in a network of control and collecting units;

FIGS. 5 and 6 show flow diagrams illustrating the transmission protocol.

DETAILED DESCRIPTION OF THE INVENTION

Below an embodiment of a protocol is described in detail, useful for thetransmission of information between nodes of a network, e.g. controlunit and collecting unit in an electric energy distribution network,where such units are combined with electric or electronic appliancespowered by the network and wherein the messages are transmitted by meansof carrier waves on a channel represented by the electric distributionnetwork. Here below the transmission protocol is described in anapplication to such a network, even though it should be understood thatthe method according to the invention has several applications. Thecollecting units combined with the collecting nodes interrogate thecontrol units combined with the control nodes and the latter transmitinformation to the collecting units. The collecting units transmit thenthe information e.g. to a control center, via radio, GSM or the like.

To illustrate operation of the transmission protocol, FIG. 1 showsschematically a simple network with a limited number of nodes or points.However complex, an electricity distribution network can be representedas a network of interconnected nodes. The principles described belowwith reference to the simple network of FIG. 1 can be appliedanalogously to extended networks.

FIG. 1 shows sixteen nodes UC1, . . . UC16 and two nodes URI, UR2. Thesecorrespond to sixteen-control units 21 (UC), combined for example withas many electric or electronic appliances connected to the distributionnetwork, and two collecting units (UR) combined for example withcorresponding transformers from medium to low voltage which power thenetwork or with other appliances combined with the network. Each unit,whether collecting or control, is assigned one univocal identificationnumber.

One embodiment of a collecting unit is shown in FIG. 2. The collectingunit 31 comprises a microprocessor 33 with a memory 41, powered by apower supply 37, which also powers (via the grid forming the networkconnecting the various nodes) a PLM (power line modem) 39 whichcommunicates with the control units via carrier waves lines L, N on thedistribution network 5.

An embodiment of the collecting unit is schematically shown in FIG. 3and indicated overall in said figure by 51. The collecting unitcomprises a microprocessor 53 with a memory, 55, powered by a powersupply 57, which also powers a PLM 59 which communicates with thecontrol units via carrier waves on lines L, N the distribution network5. The collecting unit also provides for a transmitter 61 to communicatewith a control centre, for example via the GSM system or other.

As can be seen in this simple schematic example, the network comprises aplurality of different connections so that each node can be reachedfollowing different paths. To represent the topology of the network,coverage equations are used, each of which represents a linear sectionof the network, defined via the nodes that belong to said portion. Forexample, in the case of FIG. 1 the following coverage equations can beused:

UR1-UC1-UC2-UC3  Eq 1:

UC3-UCS-UC6-UC7  Eq 2:

UC7-UR2  Eq 3:

UR2-UC8-UC9-UC10-UC11-UC12-UC13  Eq 4:

UC13-UR1  Eq 5:

UC13-UC14-UC15  Eq 6:

UC3-IUC5  Eq 7:

UC15-UC16-UC7 Eq 8:

Furthermore, it can be observed that the various nodes UC_n are allconnected to both the collecting units UR1 and UR2. In general, also forcomplex networks, for the various nodes in which the control units arearranged paths can be found that connect the nodes to several collectingunits.

To optimize the message transmission times, it is advisable for thevarious nodes with the control units to be divided into coverage groups'or lists, each of which is assigned mainly to one of the collectingunits. This means that the nodes of a certain coverage list or groupdialogue with one specific collecting unit and not with the others. Forits part, each collecting unit dialogues with the nodes represented bythe control units of the coverage list (or coverage lists) assigned toit and not with others. Each coverage list is also assigned,secondarily, to at least one second collecting unit, as an alternative.As will be clarified below, this means that operation of thecommunication system can be maintained also in the event of a faultoccurring in one of the collecting units.

In the schematic simplified example of FIG. 1 we can hypotheticallydivide the nodes, for example, into the following two coverage lists:

-   -   list 1: nodes UC1, UC2, UC3, UC5, UC13, UC14, UC15, UC16    -   list 2: nodes UC6, UC7, UC5, UC9, UC10, UC11, UC12.

Since in this simplified example there are only two collecting units,each coverage list is assigned secondarily to the other of the twocollecting units.

For transmission, the control and collecting units use messages that canhave the structure schematized in FIG. 4. In the example illustratedeach message comprises:

-   -   an initial part indicated as HEADER, which contains the bits        identifying the beginning of a message, to allow the receiver        units to recognize the message, distinguishing it from the noise        on the transmission line. The bits synchronizing and identifying        the beginning of the message can be configured according to a        known technique;    -   a message identification field, marked “MSG IDENT” in the        diagram, indicating a series of fields that permit correct        identification of the message, for example: length of the        message, coding of a command, characteristics of the message, a        TTL (Time To Live) counter etc.;    -   a section indicated “MESSAGE PATH”, consisting of a plurality of        fields ID_1, ID_2 . . . ID_K, . . . ID_N, each of which contains        the identification number of a node of the path that joins the        node generating the message to the node to which the message is        addressed. The identification numbers of the nodes are entered        in the message in the sequential order in which the nodes are        arranged along the path. The first identification number ID_1 is        that of the node that generated the message, while the last        identification number ID_N is that of the node to which the        message is addressed; it therefore identifies the recipient of        the message. This path is constructed by the node that generates        the message, for example and typically one of the collecting        units, on the basis of the coverage equations, as will be        clarified by an example below. With this sequence of        identification numbers of the nodes in the path, each message is        self defining, i.e. it contains the definition of the path it        must follow to reach its destination;    -   a section indicated as ID_next, which contains the        identification number of the next node, along the path, to which        the message must be sent. At the moment when the message is        generated and transmitted for the first time, the identification        number ID_next corresponds to the first identification number in        the “MESSAGE PATH” section. As the message moves forward by        generation of successive echoes along the path defined in the        message, the identification number ID_next is updated: each node        that generates an echo updates it with the identification number        of the next node present in the path description;    -   a body of the message, indicated by “MSG BODY”, which can        contain commands, information or other, the time of the message        or further information or fields, and which can if necessary be        constructed by adding fields during transmission of the message        from one node to another, as will be clarified below;    -   a message validation field, indicated by CRC, which contains a        validation code generated in a per se known manner, for example        with a CRC (Cyclic Redundancy Check) algorithm or other.

The general algorithm for transmission of the messages is describedbelow with specific reference to the flow diagram of FIG. 5.

The generic node M generates a message intended for a generic node N. Onthe basis of the coverage equations of the network the processor of thenode M defines the path that the message must follow to reach therecipient node. The description of the path, represented by a sequenceof identification numbers of the nodes along the path, is incorporatedin the message. Each node along the path defined in the messagegenerates an echo of the signal towards the next node. In this way thesection the message must cover before being regenerated by an echo isequal to the distance between two consecutive nodes along the path.However, if in certain operating conditions or in certain sections ofthe network the impedance is low, situations can occur in which themessage emitted by a node reaches not only the first subsequent nodealong the path, but also more distant nodes along said path. In thiscase one or more nodes along the predefined path can be skipped.

With reference to the simplified network of FIG. 1, it is assumed thatnode UR1 must send a message to node UC15 via the path indicated by PH,defined by the coverage equations 5 and 6, containing the nodes UR1,UC13, UC14; UC15.

The message will therefore contain in the definition of the path theidentification numbers

-   -   ID_UR1, ID_UC13, ID_UC14, ID_UC15        where the last identification number is that of the recipient of        the message and the first identification number is that of the        sender of the message. Before transmitting the message, the        sender attributes to the field ID_next the value of the        identification number of the nearest node along the path PH. In        the example illustrated in FIG. 1, said value will be the        identification number of the node UC13.

The message is transmitted on the network. A plurality of nodes willreceive the message, according to the topology of the network and theimpedance, variable according to the conditions prevailing on thenetwork. Each generic J-th node (of which ID_J represents theidentification number below) that receives the message falls into one ofthe following categories:

-   -   A. It is a node alien to the path;    -   B. It is a node of the path.        The processor associated with the node recognizes whether it is        in the predefined path of the message or not by reading the data        in the “MESSAGE PATH” section. If it is a node alien to the        path, it must remain completely inert. Vice versa, if it is a        node of the path, there are two possibilities:    -   the identification number of the J-th node is different from        ID_next. The node remains inert;    -   the identification number of the J-th node which receives the        message is equal to ID_next (ID_J=ID_next), i.e. it is the node        of the path nearest the node that emitted the message. In this        case the J-th node will generate a message which will be the        echo of the message received or the response to the message        received according to whether it is the recipient node of the        message (ID_J=ID−N) or an intermediate node that acts as a        “bridge”.

The echo of the message consists in repetition of the message received,in which, moreover, the following substitution is performed

ID_next=ID_next+1

i.e. in the echo of the message it is indicated that the next node thatmust be activated upon receipt of the message is the subsequent node inthe path PH contained and described in the “MESSAGE PATH” section of themessage. In practice, if the node that receives the message is the J-thnode, the field ID_next of the message arriving will contain theidentification number of the J-th node, i.e. will be

ID next=ID J

and the field ID_next of the echo will contain the value ID_next=ID_J+1.

In the echo of the message information can be incorporated or added ifnecessary by each node of the path, as will be clarified below, or theecho can be identical to the message received except for the increase inthe identification number of the subsequent node along the path.

In the example of FIG. 1, the nodes UC1 and UC13 are adjacent to thenode UR1 that generated the message. The node UC1 remains inert, as itrecognizes that it does not belong to the path. The node UC13 generatesan echo since the node UR1 has set Cnext=ID_UC13.

Since the next node along the path PH is the node UC14, the echo of themessage generated by the node UC13 will contain

I_next=ID_UC14

If other nodes, such as nodes UC2, UC14 and UC12 receive the messagegenerated by the node UR1, they remain inert, since the condition

I_next=ID_j

does not occur. In reality, the nodes UC2 and UC12 do not belong to thepath PH and therefore must not generate an echo. The node UC14 belongsto the path. However, if it generated an echo there would be anoverlapping of echoes on the line. Since it is not possible to knowbeforehand the depth of penetration of the message along the variousbranches of the network, using the algorithm described above avoids thegeneration of several echoes of the same message, at the cost of slowingdown its penetration speed towards the destination node. Said speedwould in fact be higher if, due to a particularly low line impedance,the message generated by UR1 penetrated directly along the path as faras the node UC14 or even UC15. The impossibility of knowing beforehandthe penetration depth makes it advisable, to obtain a simpletransmission control algorithm, to proceed as said in single steps,where each regeneration of the message by echo causes an advancement ofonly one node along the path.

The entire process described above is summarized in the block diagram ofFIG. 5.

The N-th node marked by the identification number ID_N (in the examplereferring to FIG. 1 the node UC15) recognizes that it is the last in thelist and therefore the recipient of the message. On the basis of thecontent of the message in the “MSG BODY” section, it will generate areply message, in which the “MSG BODY” section contains the datarequested by the message received. The path will be the same as the onefollowed by the message received, inverted. The transmission process isrepeated in exactly the same way, simply inverting the sequence of thenodes in the path.

The recipient node can receive a message containing information orinterrogation or any other useful element according to the type ofmanagement required on the network.

In the specific case of stray voltage monitoring, the end recipient ofthe message can be interrogated on the operating status of the controlunit and the voltage of the related interconnection box, or the lamppost or other component connected to the control unit.

In the specific example described above with reference to the simplesituation of FIG. 1 it has been assumed that the path described in themessage is defined by the identification numbers of all the nodesbetween the collecting unit that generates the message and the recipientcontrol unit.

This is the simplest transmission protocol implementation hypothesis,which does not take account of the greater or lesser difficulty oftransmitting the message on the channel, typically the electricitydistribution network. Given a recipient node of the message, the messagealways contains in this case a complete description of all theintermediate nodes between the unit that generates the message and therecipient control unit.

This is actually not necessary. On the basis of the line impedanceconditions, the message generated by a collecting unit can reach notonly the nearest node along the chosen path to reach the messagerecipient, but also for example the second or third node in order ofdistance. When this happens, because the transmission channel (forexample and typically represented by the electricity distributionnetwork) is particularly clean, the transmission process would beshortened if, in the description of the path, the message contained onlythe number of nodes strictly necessary.

In an improved embodiment of the transmission protocol according to theinvention, the collecting unit(s) run self-leaning or test cycles on theconditions of the transmission channel to check for example if it ispossible to transmit a message skipping a certain number of nodes andreducing the number of echoes to be generated. For said purpose messagescan simply be sent from the collecting unit to gradually more distantnodes, whose path description does not contain the intermediate nodes.Reference should be made again for example to the simplified diagram ofFIG. 1 and of the path from the collecting unit UR2 to the control unitUC12. In the simpler form of implementation the message addressed tothis control unit will always contain the description of the path viathe identification number of the control units UC8, UC9, UC10, UC11,UC12. If the system is implemented with the self-learning function, thecollecting unit UR2 can send a message to the node UC9 with a pathdefined only by the identification number of the control unit UC9. Thismessage will be received and replied to by the node UC9 only if thelatter is actually reached. The collecting unit UR2 is therefore able toestablish whether the message sent to the control unit UC9 (or toanother unit farther away) can skip the node UCS. Analogously a furthertest can be performed with a message addressed to the node UC10, whichcontains in the description of the path only the identification numberUC9 and so on. Having ascertained, for example, that the control unitUC9 can be reached by skipping the node UC8, the collecting unit UR2 cansend a message addressed to the control unit UC11 with a path describedonly by the identification, number of the unit UC9. If the unit UC11provides a reply to said message, it means that the node UC10 can alsobe skipped and so on.

Repeating this control cycle on the conditions of the transmissionchannel and therefore on penetration of the message along a certainpath, the collecting unit UR2 could for example detect that the messageto the control unit UC12 can run a skipped path defined by the sequenceof identification numbers of the units UC9, UC11, skipping units UC9 andUC10.

In an improved embodiment of the transmission protocol according to theinvention, the collecting unit(s) run self-leaning or test cycles on theconditions of the transmission channel to check for example if it ispossible to transmit a message skipping a certain number of nodes andreducing the number of echoes to be generated. For said purpose messagescan simply be sent from the collecting unit to gradually more distantnodes, whose path description does not contain the intermediate nodes.Reference should be made again for example to the simplified diagram ofFIG. 1 and of the path from the collecting unit UR2 to the control unitUC12. In the simpler form of implementation the message addressed tothis control unit will always contain the description of the path viathe identification number of the control units UC8, UC9, UC10, UC11,UC12. If the system is implemented with the self-learning function, thecollecting unit UR2 can send a message to the node UC9 with a pathdefined only by the identification number of the control unit UC9. Thismessage will be received and replied to by the node UC9 only if thelatter is actually reached. The collecting unit UR2 is therefore able toestablish whether the message sent to the control unit UC9 (or toanother unit farther away) can skip the node UC5. Analogously a furthertest can be performed with a message addressed to the node UC10, whichcontains in the description of the path only the identification numberUC9 and so on. Having ascertained, for example, that the control unitUC9 can be reached by skipping the node UC8, the collecting unit UR2 cansend a message addressed to the control unit UC11 with a path describedonly by the identification, number of the unit UC9. If the unit UC11provides a reply to said message, it means that the node UC10 can alsobe skipped and so on.

Repeating this control cycle on the conditions of the transmissionchannel and therefore on penetration of the message along a certainpath, the collecting unit UR2 could for example detect that the messageto the control unit UC12 can run a skipped path defined by the sequenceof identification numbers of the units UC9, UC11, skipping units UC9 andUC10.

This embodiment, however, maintains the concept that the messageaddressed by a collecting unit UR to a control unit UC contains thedefined path that the message (and consequently the reply to it) mustfollow. The control units do not have to perform any operation and donot have to choose in any way the path to be followed by the message

The messages that can be transmitted through the network can be ofvarious types. The following three messages can be typically used formanagement of the network.

“Train” type messages run along a path PH from the first to the lastnode defined in the message, and return to the first node which istypically a collecting unit UR. Each time the message passes from onenode to the next one along the path, the bridge node that generates theecho (at outward or return transmission) does not only increment thevalue of ID_next but adds to the message in transit significantinformation on its status. For example, in this type of “train” message,an information bit or byte can be assigned to each node of the path. Inthe case of application to the monitoring of stray voltage, each controlunit combined with the nodes of the path defined in “MESSAGE PATH”enters in the message regenerated via echo a datum which indicateswhether the respective interconnection box is at a voltage above orbelow a danger threshold. For said purpose it is sufficient to provideone information bit for each node, said bit taking on the two values “0”or “1” according to the condition of the node. The bit can be containedright from the beginning of the message, for example in the “MSG BODY”section, or can be added by each node, lengthening the “MSG BODY”section.

In this type of message, each node that generates the echo must alsorecalculate the validation code CRC, since the echo of each message isnot identical to the message received in input and therefore thevalidation is possible only if the CRC is recalculated each time.

“Interrogation” type messages: The function of this type of message isto reach a node without collecting information from the intermediatenodes along the path. This type of message is used to recover or deliverfunctional parameters from or to the message destination node. Thetransmission mode is the one already described with reference to FIG. 5.

Alarm messages: When one of the nodes in which the control units arearranged detects an alarm situation which must be signaled immediately,instead of waiting to be interrogated by the subsequent “train” type or“interrogation” type message, it immediately generates an alarm signal,which is addressed to the collecting unit to which the node, i.e. therelated control unit, is assigned. The message is addressed byindicating as the path the one followed by the last message which saidnode has received from the collecting unit. Alternatively, the alarmmessage can contain a description of a different path, which the controlunit has “seen” pass, for example a message that has passed through thenode to which the control unit belongs, but addressed to a differentnode. In theory, the alarm message can also be sent along a path thatleads to a different collecting unit from the one to which the node thatgenerates the alarm signal is assigned, since the aim of this type ofmessage is to be sent as soon as possible to the control centre to whichthe collecting units are connected.

In this way the alarm signal reaches the collecting unit very quickly,even if the individual nodes are interrogated at long intervals.

Basically two fault situations can occur:

-   -   fault in a collecting unit;    -   fault in a control unit.

The first type of fault is detected directly by the control centre towhich the collecting units are connected, for example via the lack of acommunication signal. When this happens, in order for the control unitsof the nodes combined with the faulty collecting unit to remainconnected and correctly monitored, they are re-assigned to thecollecting unit to which they had been assigned secondarily orsubordinately. For example, in the case of the simplified network ofFIG. 1, if a fault occurs in the collecting unit UR1, the nodes UC1,UC2, UC3, UC5, UC13, UC14, UC15, UC16 assigned to it will be temporarilyre-assigned to the collecting unit UR2 until operation of node UR1 isrestored. In this case it is an unavoidable choice, as there are onlytwo collecting units. When the network is more complex, the coveragelist assigned to a collecting unit in which a fault occurs can bere-assigned to a collecting unit chosen from among the many others thatare present in the network. Alternatively, the coverage list can bedivided and re-assigned partly to one and partly to the other of severalcollecting units.

The collecting units can receive in the programming phase all thecollection lists so that in the event of a fault it is easy to transmita message from the control centre, in which the various collecting unitsoperating which must compensate for the temporary fault are informed ofthis circumstance, so that they begin to manage the control unitstemporarily reassigned to them.

The failure or temporary impossibility of reaching a node represented bya control unit along the path may not prevent the message reaching theend recipient, i.e. the last node in the path. This occurs when from thenode preceding the faulty one, the message manages to penetrate as faras the second subsequent node. If this does not happen, however, forexample due to the presence of a high impedance or because twoconsecutive nodes along the path are faulty, the message does not reachits final destination and the collecting unit that emitted it mustreceive consequent information. Information must be generated also whenthe final node is reached despite the fault in an intermediate node.

FIG. 6 shows the algorithm that performs this check and which permitsattempt at transmission beyond the faulty node, signaling the abnormalsituation and/or impossibility of reaching the final node to thecollecting unit that generated the message. The block diagram is partlyequal to that of FIG. 5, since the parts relating to checking of thefault and to the fault transmission attempt have been added, whiletransmission in regular operating conditions follows the same diagram asFIG. 5.

Basically, the J-th node that receives the message the echo of which itmust send to the next node according to the path entered in the MESSAGEPATH section of the message, sends the message on the network. Thefollowing node that correctly receives the message generates an echo ofit according to the procedure already described. This echo which isreceived back also by the J-th node, can be considered a confirmation ofreception of the message regenerated by the echo of the J-th node andtransmission to the node in position ID_next. If this confirmation isnot received by the J-th node, the situation is interpreted as a faultor an interruption at the level of the node following the J-th node inthe message path.

The J-th node introduces into the message information concerning thissituation and attempts to transmit the same message, generating a newecho, to the second subsequent node, skipping the one that has notreplied. This transmission attempt involves changing the identificationnumber ID_next, incrementing it by one, so that the node that mustreceive it is the second and not the first node subsequent to the J-thnode along the path defined in “MESSAGE PATH”.

If the interrupted or faulty node can be skipped, the second subsequentnode transmits an echo of the message that represents for the J-th nodea confirmation of reception. At this point the message continues itsnormal path as far as the destination node. The only difference withrespect to the situation of no fault on the node subsequent to the J-thnode is information in the message which will be received by the node Min the return phase. This permits transmission of a fault signal to thecontrol centre and allows the collecting unit to modify the path toavoid the faulty node passing through a non-fault series of other nodesaccording to a different connection, i.e., constructing new sequence in“MESSAGE PATH” via the coverage equations. For example, if in thediagram of FIG. 1 the node UC14 were faulty, in the following messageaddressed to the node UC15 the collecting unit UR1 could use the pathUC1, UC2, UC3, UC15, skipping the faulty node.

If also the second node following J-th the node does not respond becauseit is faulty or because the message regenerated by the echo of the J-thnode does not manage to reach a sufficient penetration depth, the J-thnode does not receive confirmation of reception. When two consecutivenodes are faulty, the J-th node retransmits the message to the node Mthat has generated it, with information on the double interruption. Inthe diagram of FIG. 6 the counter K has the function of limitingthere-transmission attempt to two consecutive nodes, since otherwise theJ-th node would continue in its transmission attempts to othersubsequent nodes.

It is understood that the drawing only shows a practical embodiment ofthe invention, which can vary in its forms and arrangements, withoutmoreover departing from the scope of the concept underlying theinvention. Any presence of reference numbers in the following claims hasthe sole aim of facilitating the reading thereof in the light of thedescription and the drawings and does not in any way limit the scope ofthe protection.

Thus, although there have been described particular embodiments of thepresent invention of a new and useful Method for Transmission ofInformation Between Nodes of a Network and Network Using Said Method itis not intended that such references be construed as limitations uponthe scope of this invention except as set forth in the following claims.

1. A method for communication between nodes of a network interconnectedby a transmission channel and each node identified by a nodeidentification number comprising: (a) at least one transmitter nodeemitting at least one message to at least one message recipient nodewherein the transmitter node originates the message and the messagerecipient node represents a final destination for the message; (b) saidmessage when originated and emitted by the transmitter node comprising adescription of a path between said transmitter node and said messagerecipient node, said path being defined by the transmitter node thatoriginates and emits the message, via a sequence of node identificationnumbers along said path; (c) the nodes of the path regenerate themessage by sending it to the next node defined by said path stored inthe message; (d) each node that receives a message from a node precedingit along said path sends a confirmation of reception of the message tosaid node preceding it; (e) when a node does not receive a message ofconfirmation to its own message addressed to the subsequent node alongthe path, it makes at least one attempt at transmission of said messageto the node which, in said path, is subsequent to the node from whichthe confirmation message has not been received; (f) wherein each of saidmessages comprises an identification number of each subsequent nodealong said path to which the message must be transmitted, saididentification number of the subsequent node identifying to which nodeof the path defined in the message said message must be transmitted; (g)when a message recipient node receives said message, it generates areply message addressed to the node that emitted the message andcontaining a description of the path from the node that receives themessage to the node that has emitted the message received; (h) when anode different from the message recipient node receives a message withsubsequent node identification number different from its ownidentification number, said node remains inert; and (i) when a nodereceives a message in which the identification number of the subsequentnode corresponds to its own identification number, it generates an echoof the message, replacing the subsequent node identification number withthe identification number of the following node in the sequence of nodeidentification numbers defining said complete message path in saidmessage.
 2. The method of claim 1, wherein each node that receives amessage from a node preceding it along the path defined in said messagesends confirmation of reception of the message to said node thatprecedes it.
 3. The method of claim 2, wherein said confirmation ofreception of the message is an echo of the message, generated by thenext node and transmitted on said network.
 4. The method of claim 1,wherein after a certain number of attempts at transmission of the samemessage to consecutive nodes along the path defined in a messagereceived, the node generates a message signaling interruption of thepath.
 5. The method of claim 1, wherein said messages compriseinterrogation messages of one single recipient node, which is programmedto reply to the interrogation message with a reply message containinginformation relating to said recipient node.
 6. The method of claim 1,wherein said messages comprise control messages of all the nodes along apath between a node emitting the message and a message recipient node,said control messages being modified by each node along the path, withthe addition of at least one datum relating to a condition of each nodealong said path, and wherein said datum added by each node to saidcontrol message is stored and delivered to the message recipient node.7. The method of claim 1, further comprising: providing a plurality ofcollecting nodes and a plurality of control nodes; and dividing saidcontrol nodes into a plurality of groups, each group comprising a seriesof control nodes, each group being assigned to a collecting node and thecollecting node interrogating via said messages the control nodes tocollect information from said control nodes.
 8. The method of claim 7,wherein the path of the message is defined by a collecting node, andwherein a control node which must send a reply to a message receivedfrom a collecting node uses a path defined in one of the messagesreceived from said collecting node.
 9. The method of claim 7, whereineach control node of a group assigned is also assigned to an additionalcollecting node and wherein: in the absence of faults on the collectingnodes, the control nodes of each group communicate with the respectivemain collecting node to which they are assigned; and in the event of afault on said main collecting node, the control nodes assigned to it arere-assigned each to the respective additional collecting node.
 10. Themethod of claim 7 further comprising representing said network via aseries of coverage equations, each of which defines a sequence ofcontrol nodes connected to one another and to a collecting node, andwhich represent the topological description of said network.
 11. Themethod of claim 7, wherein when a collecting node detects a fault itgenerates an alarm message which contains as identification number ofthe recipient the identification number of a collecting node to whichsaid control node is assigned which emits the alarm message and asdescription of the path, the description of the path contained in atleast one message received from said node.
 12. The method of claim 7,wherein said collecting nodes perform test cycles on the conditions ofthe connection line with the control nodes assigned to it to verify thedepth to which a message can penetrate along a path that joins aplurality of said control nodes.
 13. The method of claim 12, wherein thepath of a message addressed to a recipient node is determined by thecollecting node at least partly on the basis of the conditions of theportion of line that joins said collecting node to said recipient node.14. The method of claim 1, wherein the path between a transmitter nodeand a message recipient node is defined by the sequence ofidentification numbers of all the nodes positioned between thetransmitter node and the recipient node.
 15. A network for transmissionof information between nodes interconnected by said network, whereinsaid nodes transmit messages using the method according to claim
 1. 16.The network of claim 15 wherein the network is an electricaldistribution network and said nodes each comprise a modern fortransmission and reception of messages via carrier waves on saidnetwork.
 17. The network of claim 15 further comprising control nodesand collecting nodes, each control node being combined with at least onepiece of electrical equipment and controlling at least one operatingparameter of said equipment.
 18. The network of claim 17, wherein saidcollecting nodes comprise means for transmitting information received bysaid collecting nodes.